I'm wondering if a person can rig up some straps with velcro or something to go AROUND the aero bars themself then put the sling straps through those.
That was kind of where I was thinking about going with this going forward. I have access to some velcro loop for tying up cables that I might try. My other option may be to just use a couple of nylon straps in an X pattern and tie a drybag to the handlebars that way. It seems like the sling may not be optimal for this particular bike/handlebar combo. I might have to just resign myself to limiting it to use on my Mukluk instead.
I may look into the Fred Bars, but from a fit standpoint, it's going to either change my aero bar position, handlebar position or both. I have my seating and hand positions pretty well dialed in so that would be a last resort.